Re: Skipping logical replication transactions on subscriber side - Mailing list pgsql-hackers

From Masahiko Sawada
Subject Re: Skipping logical replication transactions on subscriber side
Date
Msg-id CAD21AoC4jb+wjJ=Q+89A7jxcBcasD9ey3gZpKhsJUMV8v_oaxA@mail.gmail.com
Whole thread Raw
In response to Re: Skipping logical replication transactions on subscriber side  (Amit Kapila <amit.kapila16@gmail.com>)
List pgsql-hackers
On Wed, Mar 16, 2022 at 11:28 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Mar 16, 2022 at 6:03 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Tue, Mar 15, 2022 at 7:18 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Tue, Mar 15, 2022 at 11:43 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > >
> > >
> > > 6.
> > > @@ -1583,7 +1649,8 @@ apply_handle_insert(StringInfo s)
> > >   TupleTableSlot *remoteslot;
> > >   MemoryContext oldctx;
> > >
> > > - if (handle_streamed_transaction(LOGICAL_REP_MSG_INSERT, s))
> > > + if (is_skipping_changes() ||
> > >
> > > Is there a reason to keep the skip_changes check here and in other DML
> > > operations instead of at one central place in apply_dispatch?
> >
> > Since we already have the check of applying the change on the spot at
> > the beginning of the handlers I feel it's better to add
> > is_skipping_changes() to the check than add a new if statement to
> > apply_dispatch, but do you prefer to check it in one central place in
> > apply_dispatch?
> >
>
> I think either way is fine. I just wanted to know the reason, your
> current change looks okay to me.
>
> Some questions/comments
> ======================
> 1. IIRC, earlier, we thought of allowing to use of this option (SKIP)
> only for superusers (as this can lead to inconsistent data if not used
> carefully) but I don't see that check in the latest patch. What is the
> reason for the same?

I thought the non-superuser subscription owner can resolve the
conflict by manuall manipulating the relations, which is the same
result of skipping all data modification changes by ALTER SUBSCRIPTION
SKIP feature. But after more thought, it would not be exactly the same
since the skipped transaction might include changes to the relation
that the owner doesn't have permission on it.

>
> 2.
> + /*
> + * Update the subskiplsn of the tuple to InvalidXLogRecPtr.
>
> I think we can change the above part of the comment to "Clear subskiplsn."
>

Fixed.

> 3.
> + * Since we already have
>
> Isn't it better to say here: Since we have already ...?

Fixed.

Regards,

-- 
Masahiko Sawada
EDB:  https://www.enterprisedb.com/



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